Voice-Over-Internet protocol (VoIP) is a method of enabling voice communications using the Internet as the audio transport medium. All devices wanting to participate in VoIP communications need to be able to be connected to the IP network. Since radios typically do not have an IP network interface, a VoIP radio gateway is used as an interface between the radios and the IP network. The VoIP radio gateway allows radio voice communications over the Internet by performing audio encoding, audio decoding and call signaling. Audio encoding is the process of converting the analog radio signal to a digital form which can be transmitted in a IP network. Audio decoding is the process of generating the analog signal from digital audio packet received from the IP network. Call signaling refers to the control data being exchanged between the operator console and the VoIP gateway to set up the radio call.
If the VoIP radio gateway fails, there will not be any connectivity between the IP network and the radios. This may not be a desirable situation for applications requiring uninterrupted radio communications. One approach to this problem is to design a VoIP radio gateway with very low failure rate. This low level failure rate can be achieved by incorporating redundant hardware components. However, designing a gateway with redundant hardware components will result in higher cost of design and manufacturing. Apart from the higher cost per gateway, this approach does not address the issue of survivability, in that the redundancies built in will still be lost if the entire gateway is being destroyed by a catastrophic event.